Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$197.69	7.236%	$211.9948	$211.99	$212.00	$212.00
Purchase #2	$55.27	8.408%	$59.9171	$59.92	$59.90	$59.90
Purchase #3	$174.86	13.655%	$198.7371	$198.74	$198.75	$198.70
Purchase #4	$206.34	7.285%	$221.3719	$221.37	$221.35	$221.40
Purchase #5	$52.87	3.771%	$54.8637	$54.86	$54.85	$54.90
Purchase #6	$139.26	6.609%	$148.4637	$148.46	$148.45	$148.50
Purchase #7	$30.39	8.849%	$33.0792	$33.08	$33.10	$33.10
7 purchase totals =	$856.68		$928.4275	$928.42	$928.40	$928.50